Life Cycle Assessment Of An Urban Water System On the East Coast Of Australia

Abstract

The Gold Coast region of south-east Queensland (Australia) has a population of approximately 515,000 persons and is projected to increase by up to 16,000 persons per annum. This case study examined the urban water cycle of the Gold Coast under two scenarios of infrastructure provision, namely: (1) the 'Traditional' mix, as operating in 2007-8, prior to the commissioning of large-scale water recycling and desalination schemes in this region; and (2) a semi-hypothetical 'Future' mix that includes seawater desalination, rainwater tanks and water recycling (namely, 'third pipe' Class A+ to a limited number of the total households; and indirect potable reuse via a dam from the largest wastewater treatment plant in the area). By assumption, the projected future water supply needs of the region would be met largely by a combination of desalination, water recycling and domestic rainwater tanks, but only limited additional supply from dams. Life Cycle Assessment (LCA) methodology was applied to these two scenarios in an effort to identify as broadly a possible the environmental impact potentials of adopting more energy and materials-intensive future water supply alternatives in order to service a growing population. The study found that the technologically more complex options of water supply (i.e. water recycling, desalination), as well as rainwater tanks, have the potential to increase environmental impacts on a 'per unit volume of water' basis in most impact categories (including ecotoxicity, human toxicity, global warming, ozone depletion and metals depletion), compared with the 'Traditional' supply mainly via dams. Only eutrophication potential (through more advanced treatment and reduced nutrient load discharges) and freshwater extraction (through reduced reliance on dams) would be reduced, in relative terms. Wastewater treatment and associated activities dominated environmental impacts in relative terms for the 'Traditional' urban water cycle as a whole. Nevertheless, the increase in impacts due to future alternative water supplies (recycling, desalination and rainwater tanks), was noticeable in the 'Future' scenario. Achieving a balance between these opposing environmental impact potentials presents a challenge to urban water planners and operators in the context of achieving sustainability goals in the face of a growing population and/or diminishing water supplies from existing dams.